The message, delivered with a chuckle, came in an exclusive interview with "World News" anchor Diane Sawyer who asked the presumptive GOP nominee if he had something to say to the president.
Romney said Obama's "policies have not helped the American people. They have not helped get jobs, they have not helped raise incomes and they've added trillions of dollars of debt."
He was backed by his wife of 43 years, Ann Romney, who told Sawyer she also had a message for Obama. "I believe it's... Mitt's time... It's our turn now," she said.
See the exclusive interview tonight at 6:30 p.m. ET on "World News With Diane Sawyer" and 11:35 p.m. ET on "Nightline."
Last week, the Romney campaign was able to flip the Democrats' so-called "war on women" strategy by highlighting a Democratic strategist's attacks on Ann Romney for never holding a job. Ann Romney told a GOP fundraiser this weekend that the failed Democratic talking point had been a "birthday gift."
"That wasn't how I meant it," Ann Romney told Sawyer. "It was a birthday gift to me because I love the fact that we're talking about this."
Following former Pennsylvania Sen. Rick Santorum's exit from the race last week, a bruised but unbowed Romney has entered a new phase in his campaign.
So confident in his march to this summer's convention in Tampa, Fla., Romney told Sawyer he had already taken steps toward selecting a running mate, relying on a long-trusted aide to head the search committee.
"I have selected someone who has been a counselor of mine for a number of years, Beth Myers, she was my chief of staff when I was governor," he said.
Looking forward to the general election, Romney has both sharpened his attacks on the president and become a greater target.
Many of the attacks from the left center of Romney's persona as an out of touch millionaire, so rich he not only owns multiple cars but is building a garage outfitted with an elevator to hold them at a home in La Jolla, Calif.
Romney dismissed a question about whether he could relate to working people, saying Americans don't judge people based on class.
"We don't divide America based upon success and wealth and other dimensions of that nature. We're one nation under God .... This is a time when people of different backgrounds and different experiences need to come together. I happen to believe that I'm by far the best qualified in this race between myself and President Obama," Romney told Sawyer.
When asked about Obama's suggestion that Romney release 12 years of his tax returns, Romney said he had no intention of doing that.
"The president is going to try and do everything possible to divert from the attention being focused upon his record as president and the failure of his economic policies. So he's going to try to make this campaign about the fact that I've been successful, that I've made a lot of money," he said.
Dogged through the primary by his conservative challengers about his switch from being a pro-abortion governor to an anti-abortion presidential candidate, Romney honed his pro-life position, telling Sawyer he wanted the Supreme Court to overturn Roe v. Wade.
"I would love the Supreme Court to say, 'Let's send this back to the states.' Rather than having a federal mandate through Roe v. Wade, let the states again consider this issue state by state," he said, effectively ending the federal ban on abortion.
Abortion is just one issue in which Romney has had trouble with women voters, a bloc that polls find him trailing behind Obama.
In a lighter moment Romney admitted to watching — even setting his DVR to record -- Jason Sudeikis' impersonation of him on "Saturday Night Live." Romney said he'd consider appearing on the show, but it would "depend on the nature of the skit."
"I just want it to be funny," he said.